10 Surprising Facts About Your Microbiome

We’ve all heard that gut health matters—but the more we learn about the human microbiome, the more we realise just how central it is to our overall wellbeing. Your microbiome is a community of trillions of bacteria, viruses, and fungi living primarily in your gut, and it plays a role in everything from digestion and immunity to mood and metabolism.

Here are 10 surprising facts about your microbiome that highlight just how powerful (and fascinating) this ecosystem really is:

1. You’re more microbe than human
Your body contains around 39 trillion microbial cells—outnumbering your human cells! You really are walking around as a host to your very own ecosystem.

2. Your gut microbes are unique
No two people have the same microbiome. Like a fingerprint, your microbial makeup is entirely unique to you—shaped by your birth, environment, diet, stress, and more.

3. It weighs as much as your brain
Collectively, your gut microbes weigh around 1.5 to 2 kilograms, roughly the same as the human brain.

4. They talk to your brain
Gut microbes help produce neurotransmitters like serotonin, dopamine and GABA, which influence mood, stress and sleep. In fact, around 90% of your serotonin is made in the gut.

5. They digest what you can’t
Many types of dietary fibre are indigestible to us—but not to our microbes. They ferment these fibres into short-chain fatty acids that support gut lining health and reduce inflammation.

6. Antibiotics disrupt the balance
A single course of antibiotics can reduce microbial diversity by up to 30%, and the effects can last for months—or longer.

7. Your gut affects your weight
Some microbes are more efficient at extracting calories from food, influencing weight gain, insulin sensitivity and fat storage.

8. Babies inherit their microbes from mum
The microbiome is seeded during birth and breastfeeding, laying the foundation for immune and gut health in early life.

9. Diversity is key
A diverse microbiome is generally a healthier microbiome, linked to better resilience, lower inflammation and fewer chronic conditions.

10. It trains your immune system
Around 70–80% of your immune tissue lives in your gut, where microbes help regulate immune responses and reduce the risk of allergies and autoimmunity.

Takeaway:
Your microbiome isn’t just about digestion—it’s a critical player in nearly every aspect of your health. Supporting it with the right foods, lifestyle choices, and (when needed) testing can be a game changer.

Curious about your own gut health? I now use MetaExplore microbiome testing to assess not only what microbes are there, but what they’re doing—offering deeper insights and more targeted solutions.